Dielectric properties of strained (Sr,Ca)TiO3/(Ba,Sr)TiO3 artificial lattices

Dielectric superlattices of (Sr,Ca)TiO3/(Ba,Sr)TiO3 have been formed by a pulsed laser ablation technique. The crystal structure is controlled with atomic order accuracy and a large lattice stress of 0.5-1 GPa can be introduced periodically at the interfaces owing to the lattice mismatch of the constituent layers. The (Sr0.3Ba0.7)TiO3/(Sr0.48Ca0.52)TiO3 superlattice shows dramatically large dielectric constant of 900 even at film thickness of 500 Angstrom. The optimum pressure for inducing tetragonality in the (Ba,Sr)TiO3 layers and enhanced dielectric properties occurs at a lattice mismatch of 2.5-3%. (C) 1997 American Institute of Physics.